The present invention relates to a male and female coupling mechanism whereby male and female members are detachable rigidly assembled by a heat shrinkage process.
Tool assemblies employing male and female members that are assembled by a heat shrinkage process are well known. Such an assembly is shown, for example, in U.S. Pat. No. 5,311,654. As seen in FIG. 4 of ""654, a tool shank is sidably receivable into a mounting aperture when a heat source such as an induction heater is applied to a sleeve member. The heat causes the effective diameter of the mounting aperture to increase by an amount sufficient to allow the tool shank to be slidably inserted thereinto. Upon removal of the heat source, thermal contraction causes the mounting aperture to form a rigid interface, i.e. a metal-to-metal press fit, between the sleeve member and the tool shank.
With such an assembly, the cutting tool is rigidly maintained within the sleeve member in a concentric manner. However, the gripping force upon the tool shank is greater at the rear oft the mounting aperture than at the front of the mounting aperture since the sleeve member is less rigid at its front end in comparison with its rear end.
It is the object of the present invention to provide a tool assembly that significantly reduces or overcomes, inter alia, the aforementioned disadvantages.
In accordance with the present invention there is provided a tool assembly comprising a male member and a female member, wherein in a non-assembled state:
the male member has a longitudinal axis B and comprises a rear cylindrical portion having a diameter D1;
the female member has a longitudinal axis C and comprises a variable diameter bore extending rearwardly from a front end of the female member, the variable diameter bore having a front end and a rear end, the front end of the variable diameter bore having a front diameter D2 and the rear end of the variable diameter bore having a rear diameter D3, where D3 is greater than D2, and D1 is greater than D2 and greater than D3;
and wherein in an assembled state:
the rear cylindrical portion of the male member is at least partially retained in the female member and is gripped by the variable diameter bore of the female member such that the front diameter D2 and the rear diameter D3 of the variable diameter bore are equal to the diameter D1 of the rear cylindrical portion of the male member, and the axis B coincides with the axis C.
Preferably, the variable diameter bore of the female member tapers forwardly towards the front end of the female member.
In accordance with a specific application of the present invention, the female member is made of steel and the male member is made of solid carbide and in a non-assembled state the diameter D1 of the rear cylindrical portion of the male member is greater by 0.017 mm. than the front diameter D2 of the variable diameter bore and is greater by 0.012 mm than the rear diameter D3 of the variable diameter bore.
In accordance with a preferred embodiment of the present invention, in a non-assembled state the front diameter D2 of the variable diameter bore is smaller by 0.005 mm than the rear diameter D3 of the variable diameter bore.
In accordance with a specific application, the variable diameter bore has a length dimension L and a diameter dimension D, where the ratio L/D is equal to 3.
Typically, the male member is a solid carbide cutting tool.
Preferably, the rear cylindrical portion of the male member and the variable diameter bore of the female member are ground.
In accordance with one embodiment of the invention, the female member further comprises a locating portion having a screw threaded bore and extending rearwardly from the rear end of the variable diameter bore and having a diameter greater than the rear diameter of the variable diameter bore, the screw threaded bore being produced with a locating screw for fixing the axial location of the rear cylindrical portion of the male member.
In accordance with another embodiment of the invention, the female member further comprises a rear wall located at the rear end of the variable diameter bore.